1. Field of the Invention
This invention relates to keyboards for providing an electrical output signal on depression of a key and to keys for use therein. Many forms of keyboard are used or have been proposed for providing electrical outputs corresponding to the keys which have been operated. The electrical signal output may be provided, for example, by direct mechanical operation of contacts in an electrical circuit or by changing the inductance or capacitance in an electrical circuit or by use of magnetically operated devices, e.g., reed switches or Hall effect devices.
2. Prior Art
It is generally considered desirable to provide a mechanically movable key member having an appropriate tactile characteristic, that is to say appropriate feel as it is pressed, so that the operator can move the keys and knows instinctively from the fuel that the key has been properly operated. It is commonly required, with keys providing an electrical output, that a striker, e.g., a contact member should meet an abutment, e.g., a contact or contacts, but that further depression of the key, known as overtravel can then occur.
Usually overtravel is permitted by means of a relatively soft spring which permits the key top to continue movement after a striker or plunger at the bottom of the key has come in contact with a co-operating element to effect the necessary circuit operation. Thus such overtravel may be provided by a soft spring or resilient member arranged between the key top and a plunger carrying the striker or between the plunger and the striker.